Im guessing the dungeous, since they ARE at the bottom. The Chamber of secrets was probably not first created. I mean, how obvious would that look? Godric: Uhh.. Salazar, whats that? *looks down* Slytherin: Um... my secret chamber *looks around suspiciously* Seriously, not a secret!! The dungeous had to have been first.. lol..
Hogwarts staff was created in 1997.
The Room of Requirement
The diadem was hidden in the Room of Requirement
In the "Room of Requirement", a secret room located inside Hogwarts.
Hogwarts Express.
Garlic.
The Room of Requirement. Hogwarts provides the room when a student is in need of it. Hence why it is the Room of REQUIREMENT.
Muggles cannot be accepted at Hogwarts because they have no magical ability.
'Lumos' was the first spell he used willingly outside Hogwarts before his 3rd year!
By a boats.
No, the students don't need to have "Hogwarts: A History". It's not on the equipment list of the students, but it's available in the library of Hogwarts.
During The Battle of Hogwarts, Harry went to: inside the Room of Requirement, through the halls of Hogwarts, in the Shrieking Shack and in the Forbidden Forest.